Cancer vaccines and adoptive T cell transfer approaches hold promise for cancer treatment and the prevention of tumor recurrence. Whereas these therapies often increase tumor-specific T cell levels, they are often ineffective in inducing potent effector T cells and long-lived, functional memory T cells that can mediate long-term tumor suppression. This ineffective generation of tumor-specific memory T cells is possibly due to a lack of stimulation by inflammatory mediators derived from innate immune cells. Type I Interferons, including IFN-?, are inflammatory mediators induced by pathogen-derived molecules and activate innate and adaptive immune cells including CD8 T cells. Our preliminary results in a unique model system demonstrate that systemic levels of IFN-?, similar to those found during acute viral infection, greatly enhance the vaccination-induced generation of gp100-specific effector and memory CD8 T cells with anti- melanoma activity. In addition, our preliminary data show that IFN-? exerts this activity through multiple mechanisms during distinct phases of the T cell response. Our long-term goals are to understand the regulation of generation and maintenance of tumor-specific memory CD8 T cells and learn to enhance them. This proposal is in direct response to the NIH Program Announcement PA-07-255 Memory T lymphocytes in Cancer Immunology and will focus on signals throughout the immune response that culminate into the generation and long-term maintenance of therapeutic tumor-specific memory CD8 T cells. The overall objective of this proposal is to understand how IFN-? promotes anti-tumor CD8 T cell responses through mechanistic dissection of its effects on T cells and the host environment. Our central hypothesis is that IFN-? enhances the in vivo and ex vivo generation of long-lived, tumor-specific memory CD8 T cells through direct effects on T cells during the early priming/expansion phase and through host-derived IL-15 and CD27/CD70 signals during subsequent memory T cell differentiation and maintenance. This hypothesis will be tested by pursuing the following three specific aims: 1) Determine the contribution of IFN-? during the different phases of the vaccination/IFN-?-induced, tumor-specific CD8 T cell response; 2) Identify the molecular mechanisms underlying the IFN-?-induced in vivo generation of tumor-specific memory CD8 T cells; 3) Determine whether IFN-? can promote the ex vivo generation of tumor-specific CD8 T cells that have characteristics of therapeutic anti-tumor memory T cells in vivo. Overall, the proposed studies will elucidate the mechanisms underlying IFN-?-induced anti-tumor immunity and will directly lead to the development of more effective cancer therapies.